Method for providing an extension on an end of an article and extended article

ABSTRACT

An extension is provided on an end of an article having a directionally oriented microstructure by using the article end as a growth seed in a molten material compatible with material from which the article end is made. The extension is directionally solidified as integral with and as an extension of the article end and with a microstructure compatible with that of the article end.

CROSS REFERENCES TO RELATED APPLICATIONS

The following application is directed to related subject matter and isbeing concurrently filed with the present application, the disclosure ofwhich is being incorporated by reference: Ser. No. 07/922,303, filedJul. 30, 1992.

BACKGROUND OF THE INVENTION

This invention relates to growing an extension on an end of an articlehaving a directionally oriented microstructure, and, more particularly,to such a method in which the end is used as a growth seed for theextension and article extended thereby.

The reported technology for growing directionally oriented structures,including single crystals, from a molten bath of a selected material hasevolved from simple shapes and members to complex shaped articles. Aportion of such technology includes the generation in a complex shapedmold of directionally solidified or single crystal alloy articles foruse in the hot sections of gas turbine engines. The published literaturewell known to those skilled in such art has many examples of articlessuch as turbine blades and vanes provided in such a manner.

When an article, for example a turbomachinery or gas turbine engineblading member, is operated in an environment of airborne particles andparticularly in the strenuous high temperature oxidizing and/orcorrosive conditions experienced in the turbine section of a gas turbineengine, oxidation, hot corrosion, erosion, wear, low-cycle fatiguecracking and other damage can occur to such an article. Because themanufacture of such article is expensive, it is desirable economicallyto repair rather than to replace the article.

An example of a complex shaped blading member of the type referred toabove is the turbomachinery blade described in Andersen et al. U.S. Pat.No. 4,010,531 patented Mar. 8, 1977 and assigned to the assignee of thisinvention. Such a blade includes a complex hollow interior communicatingwith an open tip for cooling purposes. The disclosure of such patent ishereby incorporated herein by reference.

Through the use of the above referred to reported technology, an articlesuch as a blading member can be manufactured as a single crystal or witha directionally solidified microstructure of elongated grains. Thecombination of casting mold technology and casting procedures enablessuch manufacture. As used herein for simplicity, the term "directionallyoriented" is intended to include directionally solidified elongatedgrained structures as well as single crystal structures, the crystalorientation or growth direction of which is maintained in a selecteddirection. As is well known in the art of blading members, thecharacteristic crystal orientation in nickel-base superalloys frequentlyused for blading members is that the <001> crystallographic directionlies substantially parallel to the growth direction; designers of suchblading members can utilize that characteristic crystal orientation tominimize the elastic modulus, and therefore reduce the likelihood ofmechanical failure due to a mechanism such as thermal fatigue, along aspecified direction relative to the configuration of an article such asa blading member.

When such a complex shaped article having a directionally orientedmicrostructure is damaged, either in operation or in a portion of itsmanufacturing procedure, the problem of its repair becomes morecomplicated and difficult. This problem of repair becomes particularlyacute when a directionally oriented structure is intended to bemaintained in the repaired portion, as is typically desired indirectionally oriented articles such as airfoils, for example, bladingmembers.

SUMMARY OF THE INVENTION

The present invention, in one form, describes a method for providing anextension on an end of an article, having a directionally orientedmicrostructure, from a molten material. The extension is grown using theend of the article as a directionally oriented microstructure growthseed for the molten material which is compatible with the article-seedstructure. In one form of the present invention, the extension is grownby providing a shaping member, for example, a die having a die opening,communicating with the molten material. Fluid pressure applied to themolten material forces it into the die opening where it is contacted bythe article-seed for a time sufficient for the seed to interact with themolten material, for example, melting back a portion of the seed orenabling interdiffusion to occur. Then the article end, acting as thegrowth seed, is withdrawn through the die opening at a rate which allowsthe molten material to directionally solidify on the growth seed as anextension of and integral with the article end. Also, it has adirectionally oriented microstructure compatible with the article'sdirectionally oriented microstructure.

In another form, the die includes a hollow die extension which is incommunication with the molten material. The article end is held in thedie extension for contact with the molten material forced therein.

In yet another form, the present invention provides an articlecomprising a body portion having a directionally oriented body or firstcrystal structure and a metallurgical structure and an extensionintegral with an end of the body portion through the use of asacrificial addition secured to the end of the article prior to formingthe extension. The extension has a directionally oriented crystalstructure compatible with and extending continuous with the body portioncrystal structure. In addition, the extension has a metallurgicalstructure compatible with and metallurgically distinguishable from thebody's metallurgical structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of apparatus adapted to practice the methodof the present invention.

FIG. 2 is a fragmentary, partially sectional view taken along line 2--2of FIG. 1, illustrating the cross-section of a shaping die of an airfoilshape.

FIG. 3 is a diagrammatic presentation of an air cooled gas turbineengine turbine blade.

FIG. 4 is a fragmentary diagrammatic view of a repaired airfoil, shownwith an extension and multiple elongated grains.

FIG. 5 is a fragmentary view of the blade tip portion of an air cooledgas turbine engine blade.

FIG. 6 is a fragmentary section view of a portion of the blade tip inFIG. 5, along line 6--6.

FIG. 7 is a fragmentary sectional view of a portion of the blade tip inFIG. 6, including a sacrificial addition.

FIGS. 8, 9 and 10 are diagrammatic sectional views of the sequence ofthe practice of the method of the present invention on a hollow article.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the art of casting, fluid pressure, such as an inert gas or air, hasbeen applied within a closed container to a molten material, such as ametal, to force the molten material upwardly through a tube. A patentwhich discloses one such method and associated apparatus is Woodburn,Jr. U.S. Pat. No. 3,302,252 patented Feb. 7, 1967, relating tocontinuous casting of an article upwardly through a pouring tube into acooled mold. The cast article is continuously withdrawn from the mold.

Another portion of the casting art sometimes is referred to as the EFG(Edge-defined, Film-fed Growth) process. In that process, no externalpressure is applied to a liquid material, but capillary action within anarrow forming tube or die is relied upon to draw the liquid materialupwardly for solidification. Frequently a seed crystal is introducedinto the liquid to initiate crystal growth. Typical patents whichdisclose features of this kind of process include La Belle, Jr. U.S.Pat. No. 3,471,266 patented Oct. 7, 1969; Asano et al. U.S. Pat. No.4,120,742 patented Oct. 17, 1978; and Harvey U.S. Pat. No. 4,937,053patented Jun. 26, 1990.

In some of the above referenced patents and elsewhere in the casting artrelating to the formation of directionally solidified or single crystalarticles, seed crystals having selected crystal orientations (primaryalpha and/or secondary beta orientations) have been used. Theyconstitute starter means for solidification of an article having theselected crystal orientation.

Heretofore, the joining of components of single crystal or directionallysolidified elongated grain articles, including turbomachinery airfoils,has generally involved the use of separately cast members of selectedcrystal orientation. Such members are assembled and bonded into anarticle across an interface between the members. Giamei et al. U.S. Pat.Nos. 3,967,355 and 4,033,792 are typical of patents relating to thistype of bonding; they include showing an attempt to match crystalstructures across the bond interface.

The method of the present invention provides a new combination of stepswhich casts or grows an extension directly on an end of an existingarticle to enable repair. Through use of the article itself as the seedor starter means, the extension is provided with a crystalmicrostructure including orientation, matched with and continuous withthat of the article. In addition, in one form, the extension has ametallurgical structure generally distinguishable from the metallurgicalstructure of the article end or body, from which the extension is grown.As used herein, the term "crystal structure" is intended to mean theoverall crystal form such as a single crystal, multiple elongatedgrains, etc. and the directional orientations thereof. The term"metallurgical structure" herein is intended to include suchcharacteristics as overall chemical or alloy composition, and the size,shape, spacing and composition of precipitates, phases, inclusions,dendrites, etc. within the crystal structure. For example, Ni-basesuperalloys generally include gamma prime precipitates, spaced dendritearms and various other distinguishable phases. The crystal structure andmetallurgical structure can be determined and identified by a variety ofknown and widely used techniques including chemical or spectrographicanalysis and various x-ray and photomicrographic methods. The term"microstructure" herein includes the terms crystal structure andmetallurgical structure.

This method eliminates the need to provide a separate member as anarticle extension, to match the extension member crystal orientationwith the article to be repaired, and then to bond the extension in theproper orientation to a portion of the article as shown in the aboveidentified U.S. Pat. Nos. 3,967,355 and 4,033,792. The method of thisinvention accomplishes all such steps in one operation, providing theextension integral and oriented with the article. As will be discussedin detail below, the present invention is particularly useful inproviding an extension on an article having a hollow interior andopenings or passages communicating through an end of the article withthe hollow interior.

One form of the method of the present invention allows use of asacrificial addition on an end of the article to be repaired to minimizeinteraction, such as melt back, of the article end with a moltenmaterial from which the article extension is grown. Furthermore, becausethe damaged article end in the present invention interacts directly withthe molten material, such as in melt back, the need to pretreat orpreshape or remove substantial material from the end can besubstantially reduced or eliminated

During evaluation of the present invention, apparatus of the type shownin FIG. 1 was used. A sealed molybdenum canister 10, in this example ofcircular cross section, is provided with a resistance heater 12 ofgraphite. Within canister 10 is an alumina melt crucible 14. Through thetop of canister 10 is a shaping member or die assembly shown generallyat 16, in this embodiment including a shaping die 18 and a die extension20. The die and the extension each have an inner wall, 22 and 24,respectively, defining hollow interiors thereof and die and dieextension or shaping openings for receiving a molten material 26 frommelt crucible 14. The die and die extension are made of an alumina,commonly used in the high temperature casting art, and have crosssectional shapes matched with, but not necessarily identical to, thecross sectional shape of the article to be treated. Surrounding dieassembly 16 is a molybdenum heater 28 to assist in control of thecondition of the molten material 26 as it moves and solidifies withinthe hollow interior of die 18.

In order to pressurize the sealed interior 30 of canister 10, a fluidpressure inlet tube 32, connected to a source of fluid pressure (notshown), such as argon, is disposed through a wall of the canister.Sensing the pressure within the canister interior is a pressure gage 34,which can provide pressure data to a pressure control (not shown) forthe source of fluid pressure, to maintain pressure at a desired,preselected level, or schedule of levels, within canister 10.Temperature sensing within canister interior 30 employs a thermocouple36. Through a furnace temperature control 38, electric power to heaters12 and 28 is controlled and scheduled as desired.

The partially sectional, fragmentary view of FIG. 2 is taken along line2--2 of FIG. 1. This figure, in which the meaning of the referencenumerals coincide with those of FIG. 1, shows the shaping die 18, thedie extension 20 and the die heater 28. Each of these elements has anairfoil shaped cross section in FIG. 2, which corresponds with the shapeof airfoil article 40, in FIG. 1. However, it is to be understood thatthese cross sections may assume any desired shape as may be necessaryfor the intended repair. An extension is being grown on the airfoilarticle 40 at solidification interface 42 in FIG. 1. However, it shouldbe understood that any shapes or assemblies of shapes can be used forsuch members, depending on the shape of the article being extended andthe desired shape of the extension.

In one of the evaluations of the present invention, a gas turbine engineturbine blade, of the general type shown diagrammatically in FIG. 3, wasused. Such a blade included a base shown generally at 44, an airfoilshown generally at 46 and a blade tip 48. The blade had a hollowinterior for air cooling with cooling holes or passages such as 50communicating with the hollow, generally labyrinthine, interior. Becausesuch a blade had a directionally solidified microstructure, including acrystal structure as elongated multiple grains, repair of damage to tip48 is difficult if such microstructure is to be continued into therepair. The present invention enables growth on the blade tip of anextension having a microstructure of crystal structure and metallurgicalstructure grown from and compatible with the parent blade tip. In thisevaluation, it was desired to repair the tip portion 48 of the airfoil46 of FIG. 3 axially outwardly from broken line 52. The material fromwhich such blade was cast was a nickel base superalloy having a nominalcomposition, in weight percent, of 6.15% Al, 6.35% Ta, 4.9% W, 2.8% Re,12% Co, 6.8% Cr, 1.5% Hf, with the balance Ni, selected minor alloyadditions and incidental impurities. The microstructure of such castblade was directionally oriented multiple elongated grains.

Another, though similar, nickel base superalloy was placed in meltcrucible 14, FIG. 1, within canister 10 which was then sealed. Thenickel base superalloy in melt crucible 14 had a nominal composition, inweight percent, of 6.7% Al, 6.2% Ta, 2% Re, 10.5% Co, 16% Cr, 1.6% Hf,with the balance Ni, selected minor alloy additions and incidentalimpurities. The superalloy was melted by resistance heater 12 at atemperature in the range of about 2790° to 2905° F. under a low-oxygenargon atmosphere. With the die assembly 16, including shaping die 18 anddie extension 20, in position as shown in FIG. 1, the melt waspressurized by introducing argon under pressure through fluid pressureinlet tube 32. At a pressure of about 48 inches H₂ O, the melt was movedupwardly in die extension 20 into shaping die 18. About 50.5 inches H₂ Owas a pressure sufficient to move melt 26 into contact with blade tip 48where it was held for about 4 minutes. During that period, blade tip 48interacted with melt 26 by melting back to solidification interface 42,FIG. 1, also shown as broken line 52, FIG. 3. Furthermore, the blade tip48 acted as an oriented growth seed for melt 26 in die 18. Then airfoilarticle 40 and article end or blade tip 48 was withdrawn by movingupwardly, as shown by arrow 54 , FIG. 1, at a rate of about 0.2 inchesper minute. This allowed blade tip 48 to solidify in die 18 and grow anextension having the same directionally solidified multiple elongatedgrain crystal structure as airfoil blade tip 48. The extension wascontinuous and integral with the blade tip. Withdrawal and directionalsolidification was continued until an extension of about 0.4" wasprovided in the same configuration and crystal structure orientation asblade tip 48.

During this process, die heater 28 was used to control the temperaturein die assembly 16 and the position of solidification interface 42.Further control of the solidifying interface can be accomplished using achill in that location, not shown, as is well known and widely used inthe directional solidification casting art. Such a chill can provide assteep a thermal gradient as is desired for selected solidification andmicrostructure growth.

Because the die assembly was made of alumina, the variation of meltdepth across the airfoil shaped cross section of the die assembly wasobserved to be that as would be expected in a non-wetting system. Thisenabled positioning of the growth seed blade tip portion in the die sothat contact with the entire tip, from leading to trailing edge, wasaccomplished.

As was presented in the example above, the composition of the blade tipalloy was different from that of the alloy of the extension grown on thetip from the melt. However, the two compositions were selected so thatthe crystal structure of the extension would grow integral with andcontinuous from that of the blade tip representing the body portion forthe extension. This mode of growth is sometimes termed epitaxial growth.In the context of the present invention, this is generally a necessarycondition for compatibility between the alloy of the blade tip (or bodyportion) and that of the extension. Compatibility generally implies thatneither alloy adversely affect the other, whether by contamination,liquid metal embrittlement, formation of brittle phases at theinterface, or otherwise. Compatibility may also imply some limitation ondiscontinuities in mechanical and physical properties and metallurgicalstructure between the blade tip and the extension. Ultimately,compatibility must be measured by performance. If extensions of onealloy can be repeatably grown on articles of another alloy, if thearticle with an extension grown thereon is amenable to subsequentmanufacturing operations, and if the finished article performssatisfactorily in service, then it must be concluded that the two alloysare compatible, exceptions to the preceding generalitiesnotwithstanding. The same considerations apply to sacrificial additions.As used herein, the phrase "molten material compatible with . . . " istaken to mean a material or alloy that meets the preceding standard forcompatibility, present in its liquid form.

The article generated from practice of this invention included a bodyportion, for example, the parent blade tip having a first crystalstructure in the above example, directionally oriented elongatedmultiple grains, and a first metallurgical structure based on the alloycomposition of the body portion. Integral and continuous with the bodyportion was an extension having a second crystal structure as acontinuation of and compatible with the first crystal structure of thebody portion and having a second metallurgical structure matched andcompatible with, but distinguishable from, the first metallurgicalstructure of the body. The interface portion between the body and theextension is different from that obtained by the prior art method ofdiffusion bonding together matched, separately generated, distinctmembers. The principal distinction between the present invention and theprior art lies at the interface. In the present invention the extensionis grown epitaxially by laying down one layer of atoms after anotherfrom the liquid material selected for the extension onto the surface ofthe body. Thus, the crystal structure is continuous across theinterface. The process of the present invention further allows thesecondary grain orientation to be grown, unlike the prior art interfacebonding techniques for which such secondary grain orientation isdifficult to match in the transverse direction. The epitaxial grownregion or repaired area thus matches the original metallurgical grainstructure or orientation of the article not only in the primary, butalso the secondary, direction. The advantage over current repair methodswhich have equiaxed grains at the interface and in the repaired area issignificant in terms of mechanical and metallurgical properties sincethe metallurgical grain structure of the original article does not matchthe extension or repaired area by use of prior art methods. Even wheredifferent alloys are selected for the body and extension, there willgenerally be a gradation in metallurgical structure in the interfaceregion as a result of rapid mixing of atomic species in the liquidadjacent to the solidified structure. Even though the prior art methodis practiced with great care, there is a high likelihood of localsurface irregularities and small misalignments between the body and aseparate extension that may result in some sort of low angle boundarybetween the two parts. Likewise, there is a high likelihood thatcontaminating matter on either part will become trapped in theinterface, thereby weakening the joint.

The preceding example demonstrated that controlled growth of extensions,of the type that would be required in airfoil blade tip repair, with thesame cross-section as the parent airfoil, can be accomplished. Althoughthis example included only one end or tip extension, it should beunderstood that the present invention can be expanded to include theconcurrent repair of multiple article ends such as blade tips. Thepresent invention may also be used for repair of other single crystaland directionally oriented articles, such as turbine nozzles, shroudsand vanes.

From this example it was concluded that the crystal structure of theextension should be substantially the same as that of the existingarticle. However, it was unexpectedly found that considerable variationin metallurgical structure, notably alloy composition, between theextension and existing article is permissible, and may even bepreferable in some cases.

As a result of the practice of the present invention, the airfoil 46 ofFIG. 3 includes an extension 56, FIG. 4, from broken line 52 at which itwas desired to provide a repair. As seen in the fragmentary,diagrammatic view of FIG. 4, using airfoil 46 as a growth seed resultsin extension 56 having a compatible microstructure, in this exampleincluding multiple elongated grains, as a continuation of and integralwith that of the parent airfoil.

Another form of the tip portion of a gas turbine engine air cooled bladeis shown in the fragmentary view of FIG. 5 and the sectional view ofFIG. 6 taken along line 6--6 of FIG. 5. Sometimes this type of tip isreferred to as a "squealer tip" because under certain operatingconditions it can interfere with or rub on an opposing member toapproach a zero clearance condition. As a result of such interference,peripheral rim 58, FIGS. 5 and 6, of airfoil 60 can be abraded ordamaged. Even without such a rub condition, airborne particles andoxidation, over a period of operation, can abrade and contribute to thedamage of rim 58. The method of the present invention can be used torepair such damage by providing an extension in the manner described inthe above example. However, when rim 58 is narrow or damage extendsclose to shelf 62, interaction of rim 58, such as melt back in melt 26in FIG. 1, should be limited and carefully controlled in order to avoiddamage to shelf 62. One form of the method of the present inventionprovides use of a sacrificial addition carried by rim 58 at 64 in FIG.7. The edge or surface 66 of rim 58 in FIG. 7 is represented to beeroded, damaged and in need of repair.

Sacrificial addition 64 need not have the same microstructure as theblade tip, for example, elongated multiple grains or a single crystal.All that is required is that it be attached to rim 58 and be of amaterial which is compatible with that of melt 26. For example, if melt26 is a nickel base superalloy, addition 64 can be Ni, a Ni base alloyhaving elements which will not dilute or substantially change thecomposition of melt 26, an alloy of one of the alloying elements of melt26, etc. Addition 64 can be applied by a variety of methods well knownin the art, including flame spraying, electro-deposition, diffusionbonding of a preformed member, etc. Also, because the sacrificialaddition 64 will be melted away in melt 26 during practice of the methodof this invention, the shape of addition 64 can be any convenient one:it can be shaped as an extension of rim 58 as shown in FIG. 7, it can bea shim, sheet or foil carried by rim 58, etc. The melting away ofaddition 64 by melt 26 exposes at least the surface microstructure ofrim 58 to melt 26 enabling such surface to act as a growth seed,according to this invention. Use of a sacrificial addition 64facilitates the proper positioning of airfoil article 40 in FIG. 1 sothat when an article such as airfoil 60 in FIGS. 5, 6 and 7 is beingrepaired, the melt back line 68 in FIG. 7 is located away from ratherthan at or in shelf 62. Without such sacrificial addition, it might berequired, in order to achieve complete contact of and interaction withmelt 26, to melt back rim 56 into shelf 62.

The presentation of FIGS. 8, 9 and 10, which are diagrammatically insection, show a sequence of the practice of the method of the presentinvention in a surrounding shaping die (not shown) as in FIG. 1, inrelation to repair of an article having a hollow interior. For example,such interior can be the labyrinthine passages 70 in an air cooledturbine blade. For convenience, some of the reference numerals are thesame as have been used previously herein. FIG. 8 shows rim 58 in contactwith and partially melted back by melt 26 from previous rim edge 66shown in phantom. In FIG. 9, melt back has continued further into rim 58to melt back line 68, sufficient for the remaining portion of rim 58 toact as a growth seed for melt 26. Then airfoil 60 is moved upwardly, asshown by arrow 54 in FIG. 10, while in contact with melt 26 untilextension 56, delineated by broken line 72, is grown on rim 58 bysolidification above melt line 68 which becomes solidification interface42, as described above. If blade extension 56 is solid in some part,additional holes can be drilled therein to allow air egress or externalcommunication with the hollow interior, as desired. For example, suchholes can be generated by drilling with laser, electrochemical orelectro discharge methods well known and widely used in the art ofmaterial removal.

One evaluation of the present invention used an air cooled turbine bladeof the type shown in FIGS. 5, 6 and 7, and which had been exposed to gasturbine type operating conditions. The blade was manufactured from thesame nickel base superalloy as in the previous example. This alloyincludes in its composition Al and Hf, which when exposed to hightemperature oxidizing conditions form stable surface oxides. Suchalloying elements, and occasionally yttrium, are commonly used in nickelbase superalloys from which turbine blades are manufactured. Therefore,the exposed surfaces of air cooling passages or holes, such as holes 74in FIGS. 5, 6 and 7, were coated with surface oxides which were foundnot to interact with or melt in the molten material such as melt 26.Because such surfaces were oxides, they act as non-wetting molds. Inthis example, melt back was allowed to proceed into the blade materialin which the holes were generated. Unexpectedly, very few of the holeswere filled when contacted by melt 26, which had the same composition asthe extension material of the previous example, and their integrity wasmaintained. However, in order to avoid such non-wetting action fromaffecting other portions of the blade tip which are intended to interactwith the molten repair material, pretreatment to remove oxides,coatings, etc., such as mechanical or chemical surface treatment, can beused to facilitate article extension growth. In one form of the methodof the present invention the fluid pressure applied to the melt isselected to be adequate to move the melt into the shaping member butless than that required to force the melt into the oxide coated holes.Such pressure limit is a function of the size of the holes.

The present invention relates to using an article or member as adirectionally oriented growth seed for providing on an end of the membera distinguishable extension having a microstructure matched with that ofthe member. Such an extension is provided from a molten material whichis compatible or matched with the material of the growth seed so thatthe extension is integral with the member and has a microstructurecontinuous with that of the member. However, as discussed above, thecomposition of the member and of the molten material, and hence theextension grown therefrom, need not be identical. Selection of themolten material, for example to provide the extension with enhancedenvironmental resistance, is based on the tolerable degree of crystalstructure mismatch between the member, acting as a growth seed, and theextension, grown from the molten material. The rate of movement of thearticle end, acting as the growth seed, from the molten material is afunction at least of the fluid pressure applied, the temperature of themelt, the thermal gradient at the solidifying interface and the rate ofsolidification and growth of the extension.

It is contemplated by the method of this invention that if a moltenmaterial has a melting point lower than that of the article end actingas a growth seed, interaction between the molten material and growthseed need not include complete melting of the growth seed article end.All that is necessary is that a condition exist at the interface toallow crystal structure growth across the interface and into the moltenmaterial.

The present invention has been described in connection with specificexamples and embodiments, including those presented in the drawings. Itshould be understood, however, that these are intended to berepresentative of and not limiting on the scope of the present inventionincluded within the appended claims.

We claim:
 1. In a method for providing an extension on an end of anarticle having an outer cross-sectional shape and a directionallyoriented microstructure, the combination of steps of:providing a moltenmaterial having a chemical composition compatible with a chemicalcomposition of the article; providing a die having an internal walldefining a die opening therethrough matched in cross-section with thearticle outer cross-sectional shape; providing a die extension having ahollow interior defined by an extension wall disposed between and incommunication with the die internal wall on a first extension end andwith the molten material on a second extension end; applying fluidpressure to the molten material to force the molten material into thedie extension hollow interior through the second extension end; passingan end of the article through at least a portion of the die opening andinto contact with the molten material; holding the article end incontact with the molten material for a time sufficient for a portion ofthe article end to interact with the molten material, the article endbeing a directionally oriented microstructure growth seed; and then,withdrawing the article end through the die opening at a rate whichallows the molten material to directionally solidify in the die openingon the article end as an extension of and integral with the article endand with a directionally oriented crystal structure substantiallycontinuous with the article directionally oriented microstructure. 2.The method of claim 1 in which:the article end is a superalloy; themolten material is a superalloy having a chemical compositionmetallurgically compatible with a chemical composition of the superalloyof the article end; and, the fluid pressure is applied by a gas.
 3. Themethod of claim 1 including the additional step, prior to passing thearticle end through the die opening portion, of securing onto thearticle end a sacrificial addition of a material which is compatiblewith and will melt in the molten material to expose a surface of thearticle to molten material.
 4. The method of claim 1 in which thedirectionally oriented crystal structure of the article endsubstantially is a single crystal.
 5. The method of claim 1 forproviding an extension on an end of an alloy article having an outercross-sectional shape, a directionally oriented microstructure, a hollowinterior, and at least one passage defined by a wall through the articleend communicating with the hollow interior, wherein:the molten materialis an alloy; and the fluid pressure is applied by a gas.
 6. In a methodfor repairing an airfoil shaped tip portion of a damaged article, thetip portion having a directionally oriented microstructure of a selectedalloy, the steps of:providing a molten material compatible with theselected alloy; disposing the molten material in a shaping membermatched to the airfoil shape; holding the tip portion in contact withthe molten material for a time sufficient for the tip portion tointeract with the molten material; and then withdrawing the tip portionthrough the shaping member at a rate which allows the molten material tosolidify in the shaping member as an extension of and integral with thetip portion and with a microstructure compatible with the directionallyoriented microstructure of the tip portion.
 7. An article having adirectionally oriented crystallographic structure comprising:a bodyportion having a directionally oriented first crystal structure, saidfirst crystal structure including the size, shape, spacing andcomposition of precipitates, phases, inclusions and dendrites, and afirst chemical composition; and an extension integral with an end of thebody portion, the extension having a directionally oriented secondcrystal structure compatible with an extending continuous with the bodyfirst crystal structure, said second crystal structure including thesize, shape, spacing and composition of precipitates, phases, inclusionsand dendrites, distinguishable from the size, shape, spacing andcomposition of precipitates, phases, inclusions and dendritesdistinguishable from the first crystal structure, and a second chemicalcomposition.
 8. The article of claim 7 wherein both the body portion andthe extension are of airfoil shape.
 9. The article of claim 8 in theform of a turbomachinery blading member comprising a base and an airfoilas the body portion carried by the base, the airfoil including anintegral airfoil tip portion as the extension, remote from the base. 10.The article of claim 9 wherein:the airfoil is a nickel base superalloy;and the integral extension is a nickel base alloy.
 11. The article ofclaim 10 in which the airfoil has a crystal structure of directionallyoriented multiple elongated grains and the extension has a crystalstructure of directionally oriented multiple elongated grainssubstantially continuous with those of the airfoil.
 12. The article ofclaim 10 in which the airfoil has a crystal structure of a singlecrystal and the extension has a crystal structure as a single crystalsubstantially continuous with that of the airfoil.
 13. The article ofclaim 7 wherein the body portion is a turbine shroud.
 14. The article ofclaim 7 wherein the body portion is a turbine nozzle.
 15. The article ofclaim 7 wherein the body portion is an airfoil vane.
 16. The article ofclaim 7 wherein the body portion is a nickel base superalloy having anominal first chemical composition, in weight percent, of 6.15% Al,6.35% Ta, 4.9% W, 2.8% Re, 12% Co, 6.8% Cr, 1.5% Hf, and the balance Ni,selected minor alloy additions and incidental impurities, and theextension is a nickel base superalloy having a nominal second chemicalcomposition, in weight percent, of 6.7% Al, 6.2% Ta, 2% Re, 10,5% Co,16% Cr, 1.6% Hf, and the balance Ni, selected minor alloy additions andincidental impurities.